To conserve energy, today most of the portable, wearable, wireless sensor network and other electronic products are designed to be low in power consumption and compact in size. When the system end of a memory detects that the power supply is unstable or the system is about to enter a hibernation mode before the power is turned off, every piece of data in the memory must be backed up and stored in a backup memory element of a memory unit. However, data backup usually consumes a considerable amount of power. Therefore, unnecessary power waste may occur when backup data is already stored correctly in the backup memory element but is still being overwritten.
Moreover, when the power supply is unstable or the external power supply has a sudden power outage, the system would rely on the electric power pre-stored in the capacitor for system operations. Therefore, if backup data is already stored correctly in the backup memory element but is still overwritten, the remaining electric power would be wasted and the memory may store incorrect data once all the remaining power is run out before data backup is completed.
Therefore, there is a need to develop a non-volatile static random access memory capable of determining the need for data backup in advance. Thus, overwriting the same data is avoided when the backup data is up-to-date, and unnecessary power waste is minimized, so that the memory would contain sufficient power to perform data backup completely and correctly.